1. Technical Field
The present invention relates to the art of RF broadcasting antenna systems and, more particularly, to such a system employing a vertically oriented radiator together with a plurality of top loading wires extending therefrom, the electrical length of the wires being adjustable so that the antenna may be resonated over a wide range of operating frequencies.
2. Description of the Prior Art
Antenna systems employing an electrically conductive vertical radiator, together with top loading wires extending outward from the radiator have been known in the art. Such top loading wires have been used to increase the electrical length of such a vertical radiator and to lower its self-resonance at a particular frequency. Such a system is disclosed, for example, in the above-referenced U.S. patent application.
It is to be noted, however, that the above-noted patent application does not disclose that the top loading wires may be adjusted so as to vary the electrical length thereof whereby the antenna may be adjusted to resonate at different frequencies over a wide area. This permits a fixed length, short, and vertical antenna to be used over a range of frequencies without adding a series inductor to the antenna which would reduce the operating bandwidth and add losses and result in a higher voltage at the base of such an antenna. The use of top loading wires of variable electrical lengths improves bandwidth, reduces losses and improves the system efficiency by increasing the radiation resistance of the antenna.